1. Field of the Invention
This invention relates generally to downhole tools for use in oilfields and more particularly to downhole tools having a mobility device that can move the tool in the wellbore and an end work device for performing a desired operation at a selected work site in the wellbore.
2. Background of the Art
To produce hydrocarbons (oil and gas) from the earth's formations, wellbores are formed to desired depths. Branch or lateral wellbores are frequently drilled from a main wellbore to form deviated or horizontal wellbores for recovering hydrocarbons or improving production of hydrocarbons from subsurface formations. A large proportion of the current drilling activity involves drilling highly deviated and horizontal wellbores.
The formation of a production wellbore involves a number of different operations. Such operations include completing the wellbore by cementing a pipe or casing in the wellbore, forming windows in the main wellbore casing to drill and complete lateral or branch wellbores, other cutting and milling operations, re-entering branch wellbores to perform desired operations, perforating, setting devices in the wellbore such as plugs and sliding sleeves, remedial operations such as stimulating and cleaning, testing and inspection including determining the quality and integrity of junctures, testing production from perforated zones, collecting and analyzing fluid samples, and analyzing cores.
Oilfield wellbores usually continue to produce hydrocarbons for many years. Various types of operations are performed during the life of producing wellbores. Such operations include removing, installing and replacing different types of devices, including fluid flow control devices, sensors, packers or seals, remedial work including sealing off zones, cementing, reaming, repairing junctures, milling and cutting, diverting fluid flows, controlling production from perforated zones, activating or sliding sleeves, testing wellbore production zones or portions thereof, and making periodic measurements relating to wellbore and formation parameters.
To perform downhole operations, whether during the completion phase, production phase, or for servicing and maintaining the wellbore, a bottomhole assembly is conveyed into the wellbore. The bottomhole assembly is then positioned in the wellbore at a desired work site and the desired operation is performed. This requires a rig at the wellhead and a conveying means, which is typically a coiled tubing or a jointed pipe. Such operations usually require a rig at the wellbore and means for conveying the tubings into the wellbore.
During the wellbore completion phase, the rig is normally present at the wellhead. Occasionally, the large drilling rig is removed and a smaller work rig is erected to perform completion operations. However, many operations during the completion phase could be performed without the use of a rig if a mobility device could be utilized to move and position the bottomhole assembly into the wellbore, especially in the horizontal sections of the wellbores. During the production phase or for workover or testing operations, a rig is especially erected at the well site prior to performing many of the operations, which can be time consuming and expensive. The primary function of the rig in some of such operations is to convey the bottomhole assembly into the wellbore and to a lesser extent position and orient the bottomhole assembly at the desired work site. A mobility device that can move and position the bottomhole assembly at the desired work site can allow the desired downhole operations to be performed without requiring a rig and bulky tubings and tubing handling systems. Additionally, downhole tools with a mobility system, an imaging device and an end work device could perform many of the downhole operations automatically without a rig. Additionally, such downhole tools can be left in the production wellbores for extended time periods to perform many operations according to commands supplied from the surface or stored in the tool. Such operations may include periodically operating sliding sleeves and control valves, and performing testing and data gathering operations.
U.S. Pat. Nos. 5,186,264 to du Chaffaut, 5,316,094 to Pringle (Pringle '094), 5,373,898 to Pringle (Pringle '898) and 5,394,951 to Pringle et al. disclose certain structures for guiding downhole tools in the wellbores. The du Chaffaut patent discloses a device for guiding a drilling tool into a wellbore. Radially displaceable pistons, in an extension position, come into anchoring engagement with the wall of the wellbore and immobilize an external sleeve. A jack displaces the body and the drilling tool integral therewith with respect to the external sleeve and exerts a pushing force onto the tool. Hydraulic circuits and control assemblies are provided for controlling the execution of a series of successive cycles of anchoring the external sleeve in the well and of displacement of the drilling tool with respect to the external sleeve.
The Pringle '094 patent discloses an orientation mandrel that is rotatable in an orientation body for providing rotational orientation. A thruster connects to the orientation mandrel for engaging the wellbore by a plurality of elongate gripping bars. An annular thruster piston is hydraulically and longitudinally movable in the thruster body for extending the thruster mandrel outwardly from the thruster body, independently of an orientating tool.
The Pringle '898 patent discloses a tool with an elongate circular body and a fluid bore therethrough. A fixed plate extends radially between the bore and the body. A rotatable piston extends between the enclosed bore and the body and is rotatable about the enclosed bore. A hydraulic control line extends longitudinally to a piston between the plate and the piston for rotating the piston. The tool may act as orientation tool and include a rotatable mandrel actuated by the piston. A spring recocks the piston and a valve means for admitting and venting fluid from the piston.
The Pringle et al. patent discloses a bottomhole drilling assembly connectable to a coiled tubing that is controlled from the surface. A downhole motor rotates a drill bit and an articulate sub that causes the drill bit to drill a curved bore hole. A steering tool indicates the attitude of the bore hole. A thruster provides force to advance the drill bit. An orientating tool rotates the thruster relative to a coiled tubing to control the path of the borehole.
Another series of patents disclose apparatus for moving through the interior of a pipe. These include U.S. Pat. Nos. 4,862,808 to Hedgcoxe et al., 5,203,646 to Landsberger et al. and 5,392,715 to Pelrine. The Hedgcoxe et al. patent discloses a robotic pipe crawling device with two three-wheel modules pivotally connected at their centers. Each module has one idler wheel and two driven wheels, an idler yoke and a driveline yoke chassis with parallel, laterally spaced, rectangular side plates. The idler side plates are pinned at one end of the chassis and the idler wheel is mounted on the other end. The driveline side plates are pinned to the chassis and the drive wheels are rotatably mounted one at each end. A motor at each end of the chassis pivots the wheel modules independently into and out of a wheel engaging position on the interior of the pipe and a drive motor carried by the driveline yoke drives two drive wheels in opposite directions to propel the device. A motor mounted within each idler yoke allows them to pivot independently of the driveline yokes. A swivel joint in the chassis midsection allows each end to rotate relative to the other. The chassis may be extended with additional driveline yokes. In addition to a straight traverse, the device is capable of executing a "roll sequence" to change its orientation about its longitudinal axis, and "L", "T" and "Y" cornering sequences. Connected with a computer the device can "learn" a series of axis control sequences after being driven through the maneuvers manually.
The Landsberger et al. patent discloses an underwater robot that is employed to clean and/or inspect the inner surfaces of high flow rate inlet pipes. The robot crawls along a cable positioned within the pipe to be inspected or cleaned. A plurality of guidance fins rely upon the flow of water through the pipe to position the robot as desired. Retractable legs can fix the robot at a location within the pipe for cleaning purposes. A water driven turbine can generate electricity for various motors, servos and other actuators contained on board the robot. The robot also can include wheel or pulley arrangements that further assist the robot in negotiating sharp corners or other obstructions.
The Pelrine patent discloses an in-pipe running robot with a vehicle body movable inside the pipe along a pipe axis. A pair of running devices are disposed in front and rear positions of the vehicle body. Each running device has a pair of wheels secured to opposite ends of an axle. The wheels are steerable as a unit about a vertical axis of the vehicle body and have a center of steering thereof extending linearly in the fore and aft direction of the vehicle body. When the robot is caused to run in a circumferential direction inside the pipe, the vehicle body is set to a posture having the fore and aft direction inclined with respect to the pipe axis. The running devices are then set to a posture for running in the circumferential direction. Thus, the running devices are driven to cause the vehicle body to run stably in the circumferential direction of the pipe.
Additionally, U.S. Pat. Nos. 5,291,112 to Karidis et al. and 5,350,033 to Kraft disclose robotic devices with certain work elements. The Karidis et al. patent discloses a positioning apparatus and movement sensor in which a positioner includes a first section having a curved corner reflector, a second section and a third section with a an analog position-sensitive photodiode. The second section includes light-emitting-diodes (LEDs) and photodetectors. Two LEDs and the photodetectors faced in a first direction toward the corner reflector. The third LED faces in a second direction different from the first direction toward the position-sensitive photodiode. The second section can be mounted on an arm of the positioner and used in conjunction with the first and third sections to determine movement or position of that arm.
The above-noted patents and known prior art downhole tools (a) lack downhole maneuverability, in that the various elements of the tools do not have sufficient degrees of freedom of movement, (b) lack local or downhole intelligence to predictably move and position the downhole tool in the wellbore, (c) do not obtain sufficient data respecting the work site or of the operation being performed, (d) are not suitable to be left in the wellbores to periodically perform testing, inspection and data gathering operations, (e) do not include reliable tactile imaging devices to image the work site during and after performing an end work, and to provide confirmation of the quality and integrity of the work performed. Prior art tools require multiple trips downhole to perform many of the above-noted operations, which can be very expensive, due to the required rig time or production down time.
The present invention addresses some of the above-noted needs and problems with the prior art downhole tools and provides downhole tools that (a) utilize a mobility device or transport module that moves in the wellbore with predictable positioning and (b) may include any one or more of a plurality of function modules such as a module or device for imaging the desired work site and or an end work device or module that can perform a desired operation at the work site. The present invention further provides a novel mobility device or transport module, a tactile imaging function module and a cutting device as a function module for performing precision cutting operations downhole, such as forming windows in casings to initiate the drilling of branch wellbores. It is highly desirable to cut such windows relatively precisely to preserve the eventual juncture integrity and to weld the main wellbore and branch wellbore casings at the juncture.